It is standard practice in the pharmaceutical industry to coat or polish printed sugar tablets with waxes applied in a chlorinated or flammable hydrocarbon solvent to achieve a shiny gloss and protection for the print. Thus, typically, a print base solution containing ethanol, water, ethyl cellulose and shellac is applied to the tablets, the tablets are dried and then the dried tablets are printed. During the printing operation, talc is applied to enable the tablets to feed properly in the printing machine. After printing, the tablets are loaded into a polishing pan and a wax solution formed of various conventional waxes in a chlorinated or hydrocarbon solvent is applied over the print.
Although the above procedure has achieved some commercial success, it has been found to be lacking in several respects. The use of chlorinated solvents in the wax emulsion has been found to create a potential health problem while the use of talc in connection with the printing machines has been found to create a sanitary problem. Moreover, it unfortunately has been found that the wax coating is quite soft and does not readily protect the print. Further, if the wax coating is first applied and the tablet printed over the wax coating, the print is easily rubbed off.
It is also known to polish tablets with powdered carnauba wax. However, the shine is too hard to serve as a substrate for printing.
Accordingly, it is seen that a need exists in the tablet polishing and printing art for a wax coating and polish for tablets which will not only provide a durable shiny coating but also a substrate for printing which will retain print for extended periods.